This proposed Senior Research Career Scientist (SRS) award is to support the activities of Dr. Matthew Maciejewski, a health economist, Research Career Scientist and an established Department of Veterans Affairs (VA) Health Services Research and Development (HSR&D) investigator, allowing him expand his scientific, mentoring and service contributions. Dr. Maciejewski?s research focuses on improving care and outcomes for Veterans with obesity or multiple chronic conditions. This research is important because Veterans with obesity or multiple chronic conditions incur a disproportionate share of VA expenditures and population- based care models that effectively improve their health and health care are not yet established. To address these important populations, Dr. Maciejewski?s research particularly focuses on conducting quasi-experimental comparative effectiveness research of policies and programs designed to help Veterans with obesity or multiple chronic conditions. The goal of these evaluations is to whether existing programs and policies work as intended and which Veterans realize the greatest benefits from them. During his 20-year VA career, Dr. Maciejewski obtained HSR&D funding as Principal Investigator (PI) for 8 IIRs, 2 R01s and 1 R21 from AHRQ, an ongoing R01 from NIDA, 2 RWJ HCFO grants and contract funding from CMS that is in its 6th year. He has also been a co- investigator on three dozen other VA and non-VA grants. Dr. Maciejewski?s studies as PI helped to develop evidence on the utilization and quality of care for patients who received all or part of their care at community-based outpatient clinics and impacts of the 2002 VA medication copayment increase. Mostly importantly, Dr. Maciejewski and his team established evidence on the long-term outcomes of Veterans receiving bariatric surgery. With NIDA R01 funding, he is now examining long-term mental health outcomes that have not been widely examined in VA or non-VA surgical cohorts. In addition to Dr. Maciejewski?s research activities, he has served on national and international committees. Recent activities include service on VA HSR&D grant review panels and co-chair of the 2016 HSR&D State of the Art Meeting on Weight Management. Currently, Dr. Maciejewski serves as Chair of Partnered Evidence-Based Policy Resource Center?s (PEPReC) Technical Advisory Committee and as co-lead of the Research Data Sustainability Team responsible for facilitating continuity of administrative and clinical data available for reuse as the VA transitions to the Cerner EHR. He is a Statistical Associate Editor for JAMA and serves on the editorial board for HSR. Provision of a VA HSR&D SRS award will allow Dr. Maciejewski to enhance his research, mentoring and service contributions to the VA HSR&D mission to continue to conduct of rigorous non-randomized comparative effectiveness studies, increase his participation in local and national VA committees and train the next generation of health services researchers.